This invention relates to a trouble diagnosing device of a control system for feeding to an actuator means, control signals for actuating the actuator means so as to maintain operation of controlled means in proper conditions.
When a system producing control signals for actuating actuator means, that controls the operation of a controlled means so as to bring it in a proper operation condition, is out of order for one reason or another, the control signals at the output of the control circuit system are fed to the actuator means in the form of incorrect signals. Consequently, the actuator means executes incorrect action on the basis of the incorrect signals and possibly causes various problems. In order to prevent in advance the incorrect action of the actuator means on the basis of the incorrect signals, it is necessary to diagnose trouble in the control system from time to time, and to immediately take appropriate corrective action as soon as such trouble is detected.
In making diagnosis of trouble in the control system and electromagnetic actuators in a control system wherein the electromagnetic actuators are so constructed as to control operation of controlled means on the basis of the control signals fed from the control circuit, it may be possible to make a diagnosis of them by feeding an analog signal having a predetermined signal waveform to the control circuit and to the electromagnetic actuators and detecting an abnormality of an output signal taken from the control circuit or the electromagnetic actuators at that time.
In this case, if an analog signal is fed to the control circuit and to the electromagnetic actuators during their operation, this analog signal mutually interferes with a normal signal and puts the control circuit or the electromagnetic actuators out of order so that the controlled means makes the wrong action and invites various troubles. For this reason it seems necessary to first cut off the feed of the normal signal in diagnosing the control circuit and the electromagnetic actuators, and then feed them the analog signal. In this instance, however, it is necessary to separately provide a signal cut-off device and a signal change device which leads to a further complication of the apparatus as a whole and to inevitable lowering of realibility. This trend is specifically remarkable when the control device includes a plurality of control systems of the same kind operating in paralled to one another.
Incidentally, trouble modes of the control circuit system may broadly be divided into the following two groups; one being the trouble of the type wherein the control signal waveforms required for actuating the actuator means are not at all formed and the other being the trouble of the type wherein, through the control signal waveforms required for actuating the actuator means are actually formed and remain even when it becomes necessary to stop operation of the actuator means. Various devices may be prepared as an apparatus for diagnosing trouble in such a control system, but none of the conventional trouble diagnosing devices has been able to make easy diagnosis of the control system without hindering the operation of the actuator means and to satisfy the requirements of simple construction and high utility.